text by Natalie Wolfe, news.com.au

In what's been dubbed the "sting of the century" hundreds of people have been arrested as part of a global operation to bring down terrorist groups, mafia organisations and outlaw motorcycle gangs.

New Zealand Police say they have dealt a "huge blow" to organised crime after the major trans-national sting resulted in 35 arrests and $3.7 million in assets seized.

In Australia, more than 220 members of underworld groups were nabbed after the lengthy investigation.

"Today, the Australian Government, as part of a global operation, has struck a heavy blow against organised crime — not just in this country, but one that will echo around organised crime around the world," Prime Minister Scott Morrison said.

"This is a watershed moment in Australian law enforcement history ... Everything we've been doing has been to keep Australians safe."

According to reports in Australian media, the scheme was cooked up by an Australian Federal Police officer over beers with mates from the FBI.

What followed was Operation Ironside, where hundreds of alleged offenders were tricked into communicating via AN0M, an encrypted app designed by police.

They were allegedly caught using the app to plan executions, drug imports and launder money.

The AFP said it had busted 21 murder plots, stopped more than 3000kg of drugs from hitting the streets and seized $35 million in cash.

AFP Commissioner Reece Kershaw said the organisation had inflicted "maximum damage to serious organised crime".

"With devastating consequences to those who seek to do harm to Australians and Australia's interests, and today, Australia is a safer country because of this unprecedented AFP-led operation," Kershaw added.

More than 4000 law enforcement officers were involved in executing 525 search warrants across Australia.

"Ironside has arrested and charged who we allege are some of the most dangerous criminals to Australia," Kershaw said.

"We allege they are members of outlaw motorcycle gangs, Australian Mafia, Asian crime syndicates and serious and organised crime groups.

"We allege they've been trafficking illicit drugs into Australia at an industrial scale."

Despite the investigation running for years, and arrests being made intermittently, Kershaw said the alleged criminals had no idea they were being targeted.

"Let me be clear. When you get access and it will come out in court, you'll see that all they talk about is drugs, violence, hits on each other, innocent people who are going to be murdered," he said.

"[The texts] would be like, 'I need 1000 kilos at this price.' Very brazen. No attempt to hide behind any kind of codified kind of conversation ... including 'we'll have a speed boat to meet you at this place...'"

The app also helped police stop a mass shooting of a family of five, orchestrated by organised crime.

"That particular case will come out later on where they planned on using a machine gun and potentially at a cafe where people would have been no doubt harmed," Kershaw said.

"We were able to, with the cooperation of that particular state police force, take out that individual before they were able to do that."

Police this morning gave new details about our Operation Trojan Shield that involved three major organised crime investigations and targeted the importation, sale and supply of methamphetamine, as well as money-laundering activities.

More than 300 NZ staff - including National Organised Crime (NOCG), Armed Offenders Squad, Special Tactics Group, Asset Recovery, High Tech Crime and Auckland, Waikato, Bay of Plenty, Central and Wellington District staff - executed 37 warrants yesterday.

As of last night, 35 people had been arrested - they had appeared at the Auckland District Court and Hamilton District Court this morning facing a range of drug-dealing and money-laundering charges.

Senior members of the Comancheros in Waikato, Mongrel Mob in Waikato and the Head Hunters were among those arrested.

More than 900 charges have been laid. There were still outstanding arrests to be made, National Organised Crime Group director Detective Superintendent Greg Williams said.

One of the police operations - dubbed Operation Van - had specifically targeted the trans-national organised crime group linked to the Comancheros.

Williams said these groups had been "preying" on some of New Zealand's most vulnerable communities.

As part of the operation, up to 8.6kg of meth had been seized at the border.

Large bags of cannabis, multiple kilograms of iodine, four firearms, 14 vehicles and motorbikes, more than $1 million in cash and a number of mobile phones had also been seized.

In the past three years, NZ Police had found up to 20 organised crime groups that had been carrying out crime across international borders.

"This is a stunning piece of work," Williams said of the operation carried out by authorities both here and overseas.

"We believe the termination of these operations will have a significant impact on New Zealand's organised crime scene."

- Additional reporting, NZ Herald